There is a huge difference between significant voter fraud (which has never been found, anywhere or anytime) and it just taking so long to count the unprecedented number of mailed-in ballots, due to the fear of catching Covid standing in a massive line. Every ballot cast in accordance with the appropriate state law(s) should be counted, regardless of how long it takes. That is the very foundation of a Constitutional Federal Republic. A lot of people also forget, that election laws are a state right and they vary from state to state. Here's a good link that shows those different laws.
VOPP: Table 11: Receipt and Postmark Deadlines for Absentee Ballots